Electric motors are widely employed in various fields of technology such as robotics, industrial machines, toys, tracking systems, electric vehicles, vehicle subsystems (e.g., power steering subsystems). Controlling the electric motor, for example, to reach a target position, to spin at a target velocity or to provide a target torque, has long been a challenge. Electric motor control systems and methods may control any one of the position, the velocity or torque of the motor or any combination thereof the position, the velocity and torque.
U.S. Pat. No. 5,410,234 to Shibata et al. entitled “Motor Drive Control Apparatus”, directs to a motor control system for controlling the position of a motor where the coils are connected in a star configuration. In the system directed to by Shibata, the current position of the motor is subtracted from a position command to determine a positional error amount. A speed command is generated in a speed command calculation section according to the positional error. Furthermore, the current speed of the motor is determined in a speed detecting section. A speed error is determined by subtracting the current speed from the speed command. A torque command determined employing a proportional plus integral control calculation with respect to the speed error in a speed calculation section. A phase current command calculation section determines command values of the currents for two of the phase windings (i.e., since when the coils are connected in a star configuration the current in the third phase is the sum of the currents in the other two phases). Also a current detector determines feedback currents for the two phases, and the difference between the feedback currents and the currents command generates a current error. The current errors are subjected to a proportional plus integral control calculation, the current of the third coil is determined and a PWM control section determines the voltages to be imposed on each coil. These voltages are then amplified and provided to the coils. The system directed to by Shibata further includes at least a current feedforward which generates a voltage added to the respective voltages of the phases according to current command values and an impedance model of the motor. The system directed to by Shibata further includes a torque feedforward and a position feedforward.